1. Field of the Invention
The present invention relates to a method for servo-controlling when a reproduction for non-real-time data or real-time data of audio or video stream is requested to a multi-session disk, and to a disk reproducing apparatus using the method.
2. Description of the Related Art
Shown in FIG. 1 is a general optical disk device connected to a host such as a personal computer, comprising an optical pickup 2 for detecting recorded signals from an optical disk 1, an R/F unit 3 for outputting binary signals and serve error signals TE and FE through combining signals reproduced from the optical disk 1 by the optical pickup 2, a digital signal processing unit 4 for processing the binary signals received from the R/F unit 3 to restore digital data, an interfacing unit 5 for transmitting the restored digital data to a host such as a personal computer, a sled motor 10 for moving the optical pickup 2 across tracks on the disk 1, a spindle motor 11 for rotating the optical disk 1, a driver 7 for driving the sled motor 10 and the spindle motor 11 to rotate, a servo unit 6 for providing control input to the driver 7 and the pickup 2, a microcomputer 8 for supervising overall operation of the servo unit 6 and the digital signal processing unit 4, and a memory 9 storing data for the microcomputer 8 to use for supervising operation.
When a data reproducing command is received from a connected personal computer through the interfacing unit 5 after the optical disk 1 is inserted into a disk tray, which is a part of the optical disk device mechanism, the optical disk 1 is clamped by a clamping means, and the optical disk device of FIG. 1 reads out recorded data after the following data-type-dependent servo-controlling operation.
There are two types of data request from a host as shown in FIG. 2. One is a xe2x80x98playxe2x80x990 command for requesting real-time data such as a audio stream, the other is xe2x80x98readxe2x80x99 command for non-real-time data. The operand codes are described in FIG. 2 for several commands belonging to the two types.
When the host connected to the optical disk device of FIG. 2 through the interfacing unit 5 sends a read-type or a play-type command, the optical disk device discriminates the type of a received command at first based on the operand code contained in the received command, then adjusts a reproduction speed based on the discriminated type.
FIG. 3 shows a flow example of a conventional data-type-dependent servo-controlling method, which is explained in detail.
If a read-type command requesting non-real-time data is received from the connected personal computer through the interfacing unit 5 (S10), the microcomputer 8 reads the operand code of the received command, interprets the received command as read-type for non-real-time data, sets parameter values for allowable high speed (S11) to the servo unit 6 to conduct high-speed reproduction.
If the received command is play-type, the microcomputer 8 identifies that the received command is requesting real-time data after reading its operand code, then sets values of servo parameters for low speed, for example 1X or 2X to conduct reproduction in real-time.
After setting parameters for low or high speed, the microcomputer 8 determines from the received command a target location in which the requested data are written (S12), then moves the pickup 2 to the position ahead of the target position by one or more data blocks (S13) in consideration of a possible miss in jumping to a physical track targeted by calculation of jump tracks. FIG. 4 shows such a jumping example.
In FIG. 4, the target position xe2x80x98Tpxe2x80x99 is located in a logical track #5 of a session #4, so that the pickup 2 jumps, under the control of the microcomputer 8, to a position xe2x80x98Tp-Nxe2x80x99 ahead of the target position Tp by N blocks and reads data recorded along physical tracks from that position xe2x80x98Tp-Nxe2x80x99. The microcomputer 8 extracts sub-Q channel data from the read data (S14). The extracted sub-Q channel data consists of sync data of two bits S0 and S1, control data, address, data, and parity codes. The second most significant bit (MSB) b2 indicates whether a corresponding data block has real-time audio data or non-real-time data. Therefore, the microcomputer 8 reads the control bit b2 and identifies the type of data block (S15), which is positioned one or several blocks ahead of the target block, according to the current sub-Q channel data. If the read control bit b2 indicates that the data type is real-time audio, the microcomputer 8 considers the received read-type command to be inadequate, thus, sends a response informing mismatch of data type to the personal computer (S16). If the read control bit b2 indicates non-real-time data, the microcomputer 8 moves the reading point to the target position xe2x80x98Tpxe2x80x99 (S17) as maintains the current servo parameters set for high speed in the step S11. When the reading point is exactly on the target position xe2x80x98Tpxe2x80x99, the microcomputer 8 starts to transmit the data being reproduced at high speed to the personal computer (S18).
However, although the control bit b2 of the block ahead of the target position indicates real-time data, the block of the target location may be different in data type from the preceding block. Therefore, if preceding block is real-time data and the start target block is non-real-time data, the microcomputer 8 re-sets the values of servo parameters to increase speed abruptly and instantaneously, which causes excessive stress to a servo mechanism as well as a time delay of data reproduction. In addition, if the accessed sub-Q channel of the data block preceding the target position is partly damaged, the blocks after the target position are not even tried to read although their data can be reproduced normally.
It is an object of the present invention to provide a servo control method of an optical disk device being able to set a reproduction condition to be adequate to the type of data to reproduce in advance based on the information of table of contents (TOC) written in a lead-in area of a disk before jumping to a target location, when a data requesting command is received from a host such as a personal computer.
A servo-control method using the information of table of contents according to the present invention, reads information of a table of contents written in a disk when a data-requesting command is received from a connected host; distinguishes the type of data recorded in a target location based on the read information of the table of contents; checks whether the distinguished type is corresponding to the command type; and re-sets or maintains current parameters for servo-control operation if the distinguished type is matched to the received command, so that a servo-control mechanism is adjusted to the type of the requested data before a pickup starts to move to the target location.